This invention relates to a method and apparatus for aligning tubulars.
During the construction, repair and maintenance of oil and gas wells it is necessary to connect a plurality of tubulars. Conventionally this is achieved via screwed connections.
In order to screw the tubulars together it is usual to hold a lower tubular having an upwardly facing socket in slips in the rig floor. The downwardly extending pin of the next tubular is then aligned with the socket. The tubular is then lowered into position and the upper tubular rotated to the desired torque to make the connection.
It is important that the pin should be correctly aligned with the socket prior to lowering the upper tubular since, if this is not the case, the tubular being lowered can damage the thread of the socket which can prevent satisfactory connection.
One known apparatus for aligning tubulars comprises a positioning head which is mounted on a telescopic arm which can be hydraulically extended and retracted and pivoted in a horizontal plane to position the tubular.
This apparatus is actuated remotely by a skilled operator who has a control panel with a joystick. This apparatus is very satisfactory. However, time is critical in the oil and gas industry and even a few seconds saved in each connecting operation can amount to a very significant overall cost saving.
With this in mind the present invention provides a method for aligning tubulars, which method comprises the steps of:
a) securing a lower tubular in slips;
b) aligning an upper tubular with said lower tubular with a remotely actuable apparatus;
c) memorising the position of said stabbing guide when said upper tubular is aligned with said lower tubular;
d) connecting said upper tubular and said lower tubular;
e) releasing said slips;
f) lowering said upper tubular and said lower tubular;
g) securing said upper tubular in said slips;
h) gripping a tubular to be connected to said upper tubular in said apparatus;
i) causing said apparatus to move said tubular to said memorized position;
j) adjusting the position of said tubular, if necessary; and
k) connecting said tubular to said upper tubular.
The ability to automatically bring a tubular to its previous optimum position can save seconds on making each connection. Furthermore, it is not unknown for a tired operator to lower a tubular inappropriately with damage resulting to both the pin of the tubular being lowered and the socket of the tubular in the slips. The present invention reduces the probability of this happening with true tubulars where the alignment positions of each tubular will be approximately the same.
Whilst new tubulars are relatively straight this is often not the case for old and rental tubulars which may have been used on multiple occasions and rethreaded and/or shortened due to previous damage. It will be appreciated that although the position of the socket of the tubular in the slips may be reasonably constant the position of the apparatus may have to be varied significantly to ensure alignment of the pin and socket. In these cases the method of the invention is less advantageous although it does provide a first approximation to moving the tubular to the desired position.
Step (c) may be carried out before step (d) or after step (d). Furthermore, the threads of the upper tubular and the lower tubular may be partially made up before step (c) and then fully made up after step (c), i.e. step (c) may be carried out part way through step (d).
Preferably, the memorized position can be adjusted where desired. This may be appropriate if the initial position was memorized using a tubular which was not true.
The present invention also provides an apparatus for aligning tubulars, which apparatus comprises a remotely controllable head adapted to guide a tubular, characterised in that said apparatus is provided with sensing means responsive to the position of said head, means to memorise a position of said head, and means operative to return said head to said operative position.
Preferably, said apparatus comprises a telescopic arm which supports said head.
Advantageously, said sensing means comprises a linear transducer which is associated with said telescopic arm.
Preferably, said linear transducer forms part of a piston-and-cylinder which is used to extend and retract said telescopic arm.
Advantageously, said telescopic arm is mounted on a rotor which is pivotally mounted on a base.
Preferably, said rotor is pivotable by expansion and retraction of a piston-and-cylinder assembly mounted on said base.
Advantageously, said sensing means comprises a linear transducer which is a associated with said piston-and-cylinder assembly.
Preferably, said linear transducer forms part of said piston-and-cylinder assembly.
Advantageously, said telescopic arm is movable between an operative position in which it is generally horizontal and an inoperative position in which it extends upwardly, preferably vertically.
Preferably, said apparatus further comprises a remote control console having a xe2x80x9cmemoryxe2x80x9d button which, when actuated, will memorise the position of said head and a xe2x80x9crecallxe2x80x9d button which, when actuated, will return said head to its memorized position.